Experiments are planned to determine the stoichiometry of electron transfer using, 2,6-dichloroindophenol and potassium ferricyanide as the respective electron donor and acceptor, and monitor the changes in the Cu(II) electron spin resonance signal. Estimates of the midpoint potential of DBH can be made through dye equilibration with DBH by determining the relative percentage of reduced and oxidized forms of each reactant at equilibrium. Values for the midpoint potential of DBH can be more precisely determined by potentiometric titrations. This technique also allows the determination of a number of electrons transferred to DBH as a unit. Samples could be removed to electron spin resonance tubes at various points during the titration to correlate changes in Eh with changes in DBH oxidation. Another interesting area to be explored is the equivalence of DBH subunits. Although a few investigators have examined this question, subsequent evaluation of their results suggests that they were working with impure preparations of DBH. End group analysis and cyanogen bromide cleavage are the methods of choice to investigate the equivalence of DBH subunits.